Workflow

07/29/2011

In the good ol' days, before data collectors were in wide spread use, we used to get our existing topo on paper. We'd have to throw it over a big ol' digitizing board and trace it with a puck. This was referred to as digitizing which was a very time consuming task. Later, we were able to have the paper scanned, insert the image into AutoCAD, scale it up, and trace it on screen. This was referred to as "heads up digitizing" which was a lot more efficient and faster.

I've coined this term "heads up grading" for those who give up the paper, scale, and calculator way of grading to use the grading tools in Civil 3D instead. The example presented in this post will show how quickly and efficiently one can arrive at a grading solution using this method. If there are any fundamental concepts in this post that you do not understand, please refer to Mastering Civil 3D by Richard Graham & Louisa Holland.

The illustration below shows a parking lot. The purpose of this exercise is to grade the parking lot which feeds onto a proposed road. The linework for the parking lot is being represented by a feature line in a site named "Parking". There are no elevations applied. The proposed road is represented by a corridor.

Create Grading Setup

Add the back of curb feature line as a break line to a proposed surface named "Parking Temp". Associate a surface style that shows contours. Configure a mid-ordinate distance of 1 (don't argue with me).

Add surface spot elevation labels. As you grade the parking lot, these will automatically update.

Extract the back of curb feature line from the corridor and apply a style with the highest priority for split point resolution; maintain its dynamic link with the corridor. Since the parking lot back of curb feature line meets this corridor back of curb feature line, the match grade elevations will always be maintained even after the corridor is updated.

Grade from Corridor

Obviously the grade has already been set at the road. Using Elevation Editor, we'll grade from the road to the end of the east curb return using a 6% grade. For the west curb return, use a grade of 4.5%. You can try different values. The surface, contours and labels automatically update as you enter the values into the elevation editor. Or you can manually enter an elevation for that point.

Focusing on the east (high) side of the parking lot, we'll grade the next three segments on the feature line.

Grade down at 2% to the beginning of the curb return.

Grade up at 1% for the next two segments until the southeast corner of the parking lot is reached.

This is the elevation we will hold for this parking lot corner.

In the Interim

Let's try out the scenario of sheet flowing at 2% diagonally across the entire parking lot. This will require a feature line intersecting this corner of the parking lot and positioned to project a grading object across the parking lot.

Position this feature line to be perpendicular to a line drawn from this point of the parking lot to the opposite point which will be the low point. Place the feature line in a site named "Interim" and set its elevation to 98.99.

To project a -2% slope in the northeast direction from this feature line, open up the Grading Creation Tools and configure a grading group:

Set the site to "Interim".

Create a grading group named "Interim".

Turn on the Automatic Surface feature & configure a no display style.

Using a "by distance" grading criteria, we can create a grading object that projects for a distance of 300' and a grade of -2%.

Next we'll use the "Interim" surface to assign elevations to the back of curb feature line.

Results:

At the north turn out, the back of curb will be wrapped up by raising the northwest elevation to 95.35.

What's Happening Inside?

To model the inside of the parking lot, a grading group will be applied. Open the Grading Creation Tools:

Set the site to "Parking".

Create a grading group called "Parking Final".

Configure grading group to generate a surface using a contour style.

Set the style for the "Parking Temp" surface to a no display style.

Three types of criteria will be generated to model the top, face, and gutter pan.

The beauty of using grading groups is that if you regrade the top of curb, each grading object is regenerated using its criteria based on the top of curb feature line elevations. If the gutter criterion is only required on one side of the parking lot, you can supply a start and end point for it. The pavement can be filled in with an infill.

Results:

Finito!

This took minutes. The contours are generated and the grading annotation is done. Perhaps a minute or two could be taken to arrange the spot elevation labels. But if the grading needs to be revised, once the feature line is edited, all the grading, surfaces, and annotation will update. And, incidentally, the curb in the corridor at the entrance can be wiped down by adding sections at the entrance and decreasing the curb height dimension in Section Editor.

Parking lot grading can get a lot more complicated than this. Combinations of these grading tools can be used to arrive at a solution. Just formulate a plan of action before you start. Just remember as you are heads up grading:

Keep your interim grading groups in separate sites.

Give your sites, grading groups, & surfaces relevant names.

Use spot elevation labels; these will update instantly and it's easier to identify elevations than using the elevation editor.

Use grading groups for curb & gutter. Feature lines created by stepped offset do not automatically update.

Be aware of your feature line style priority for split point resolution.

Remember, corridors can work with site grading too! Extract feature lines for site grading reference and define those entrances.

07/12/2011

Why should you grade with Civil 3D? Because there is a tremendous chance for disconnect between the eyeball, the scale, the calculator, the pencil, the paper, what the CAD person perceives he is looking at, the typing of text, the manual creation of the profile, the manual rendering of contours not only because of the chance for human error, but because grading is a 3-dimensional task that has traditionally been done with 2-dimensional tools. And how many times in the history of land development have expensive field correction measures been taken because of an error?

This post is about grading cul-de-sacs obviously. I have sensed people's discomfort in grading cul-de-sacs because they think they need to have the grades designed before generating the cul-de-sac portion of the corridor. Then out come the scales, calculators and pencils again, with the individual arbitrarily "trying" elevations and a range of grades to see what scenario would work best.

I will be the first one to say that you cannot take the designer out of the design. So, here is a demonstration of grading a cul-de-sac in Civil 3D by a designer.

Identify Proposed Drainage Scheme for Cul-de-Sac

In the example below, the road has been graded with a corridor up to the throat of the cul-de-sac. By the looks of the existing terrain, it seems to be a logical plan to divert the drainage the low area on the north side of the cul-de-sac. Taking the elevations of the corridor at the cul-de-sac throat into consideration as well as the existing terrain around this cul-de-sac, I decide on a low point elevation of about 92.00. Instead of reaching for my scale, calculator, and pencil, I'm creating a feature line tangent to the location of my low point and assigning an elevation of 92.00 to the entire length.

So why did I just create a low line instead of a low point? Because I'm going to use this low line to project a 2% slope across the cul-de-sac so that I can analyze potential grades affecting the cul-de-sac as a whole in terms of contours. If I am unhappy with my results, I can raise or lower the line, change the slope of the line, or change the slope of the resulting grading group thereby forcing an update to the surface and generating new contours with each change.

Create Interim Grading Surface for Cul-de-Sac

Using a distance slope criteria, I'm creating a grading group to automatically generate a surface projecting at a grade of 2% across the pavement at 120', enough to cover the expanse of the cul-de-sac. This grading group will be dedicated to this cul-de-sac only. If there are other cul-de-sacs in the project to grade, I would create grading groups for each of them. Notice in the illustration below, that I am applying a style that doesn't display. I will display the contours affecting the construction of the road using the corridor, not the grading object. In just a few more steps, you'll see how this will happen.

The next piece of the puzzle involves creating a feature line up the center of the cul-de-sac bulb and assigning it the elevations from the grading group surface. We will use this as a target to transition the ETW points of the assembly so we can finish off the cul-de-sac.

Notice in the previous pics that my edge of pavement alignment has already been created. Now I'll create a surface profile using this alignment and the grading group surface just created. I will use this profile in the baseline defining the cul-de-sac.

Add Cul-de-Sac Grading to Corridor

Now I'll add the baseline to my corridor, configure a curve frequency of 5', and add the feature line as a horizontal and vertical target.

I left intentional gaps so that I could transition the cul-de-sac back into the road when I'm finished with my analysis. The contours will clean up in the gaps when I fill in the gaps with the final baselines. I can shrinkwrap the corridor after I fill in the gaps eliminating contour generation outside of the sidewalk.

Modifying the Grading Scheme

I'd like to hold my low point but change the cross slope of the cul-de-sac to 2.5%.

After applying the new grade, assigning the new elevations to the target feature line, and regenerating my corridor, I have this:

If I decide to stick with this design, I would now fill in the gaps.

Transitioning the Cul-de-Sac into the Crowned Roadway

I'll fill in the gaps by going back to the profile view, creating a layout profile with two important segments. The inside points of these segments match grade with the grading group profile. The outside points match grade with the crowned roadway. The length of each segment will be the transition length. The segment that connects the two is disregarded.

Also, the target feature line must be edited so its endpoint matches elevation with the crowned roadway.

Add a baseline to the corridor with the two regions depicted by the two tangents in the profile. Adjust curve frequencies to 5' and target the feature line in the center of the cul-de-sac.

Finishing Touches

My next step may be to apply reverse curb & gutter to the south side of the cul-de-sac. I would do this with the section editor to the appropriate station range applying a positive slope to the gutter pan.

After the grading of the overall surface is finished, I could apply smoothing to the surface in small areas to improve the aesthetics of the contours. Use surface spot elevation labels for annotation (not pictured). If you revise the grading of the cul-de-sac, they automatically update.

Using the tools of Civil 3D, I just arrived at a grading solution for this cul-de-sac in a matter of minutes. If any of the grades need revising, I have set up models within the corridor that can easily be manipulated for analysis which will assist me in being confident that my new solution will provide positive drainage.

06/28/2011

Civil layers are the worst. I've seen templates that contained over 700 layers. How can anyone keep track? Now, enter into Civil 3D. Unless you want all of your objects on layer zero, you'll have to grasp the difference between object layers and component layers.

Many people have blogged about the differences. When I encounter users who are not familiar with Civil 3D and I start to introduce the concept of object and component layers, there can be much confusion.

The example I usually use to explain the difference is that of using an external reference. When you insert it, the current layer is the one it resides on. If you freeze that layer, the whole external reference disappears. This layer represents an object layer (i.e. those layers configured to objects and labels in Drawing Settings), except you don't have to set an object layer current before creating an object; it's preset.

However, if you keep the insertion layer on (object layer), you can turn off individual layers containing contours, alignments, edge of pavements, and utilities to affect the display of individual items internal to that external reference. These individual layers represent component layers (i.e. those layers configured in styles). These layers can be managed with layer states.

Although you'll want to manage the display properties of your objects with styles, you may need to control visibility with layers when you are plotting multiple plan types from different layouts in the same drawings. There is no way to automagically change styles per viewport. So detailed layers are important.

So back to the subject of object layers:

Instead of adding over 60 layers to cover every object layer type on the list, why not just create one layer for all objects and continue controlling component layers in the model with styles and per viewport with layer states?

05/19/2011

Yesterday I posted on the subject of creating retaining wall corridors. So how would we create top of wall/bottom of wall labels?

Code sets labels work well in section, but not in plan. I use alignment labels sets that reference profile geometry points.

Create two label sets: Top of Wall and Bottom of Wall. Each label set will reference a different alignment.

For the Top of Wall label set, create a label style that references profile geometry points. My style for this is called TW and contains the text "TW=", the profile elevation, and the leader.

For the Bottom of Wall label set, create a label style that references profile geometry points. My style for this is called BW and contains the text "BW=", the profile elevation, and no leader.

The top of wall has been designed with the Top of Wall profile which has actual PVI's. The bottom of wall profile was created with a surface profile so the PVI's will not coincide. However, if you insert PI's on the alignment adjacent to the top of wall PVI points, this will pull in the bottom of wall labels since a PI can double as a profile geometry point.

The top of wall profile represents the high grade behind the top of wall. If this is the elevation you want in your label, then all is well. However, if you want the actual top of wall elevation in your label and there is an elevation difference between the top of wall and the high grade, then create an expression that will take that elevation and add the elevation difference, and then use that in your top of wall label instead.

Apply the label sets to each alignment. Drag them to a desirable location.

05/18/2011

I've seen a couple of different ways people use to create retaining walls in Civil 3D. More times than others, I see people creating a grading group representing their retaining wall, generating a surface with it, and pasting it into their site surface. It generates contours which is the desired result. This is a fairly quick and simple method.

I prefer to create a more BIM-like retaining wall with a retaining wall assembly. My reasons for using this method are:

Retaining wall assemblies recognize when they are in cut or fill and will shift codes around accordingly.

Retaining wall subassemblies have adjustable parameters.

Retaining wall code sets can be applied which not only affect the display of the wall in plan and model, but apply elevation labels automatically in section.

The top of the retaining wall can be controlled with a profile which makes it very easy to visualize and design the top of the wall in comparison with a surface. Also, when the proposed surface, top of wall profile, or retaining wall parameters change, the retaining wall and composite surface update.

Here are the steps:

Grade your proposed site out to the location of your wall to generate a proposed surface.

Create two alignments: one along where the proposed grade (P) will intersect the wall and the other along where the existing grade (E) will intersect the wall.

Create surface profiles and the profile view for the alignment representing the high side of the wall: Alignment P will use the proposed surface and Alignment E will use the existing surface.

You may superimpose the other alignment's profile into the profile view for visualization purposes. You may also temporarilly remove the vertical scale exageration from the profile.

Layout the smooth grade for the top of the wall. This will be the "hook in" point on the subassembly which is where the high surface ties in. The distance between the "hook in" point and actual top of wall is adjustable in the subassembly parameters.

Create a corridor using an assembly created with an appropriate retaining wall subassembly. The baseline will be based on Alignment P. You will configure the existing surface and the Top of Wall profile in as targets.

Create a corridor surface using the RW_Hinge and RW_Front feature lines in the corridor. RW_Hinge will always be where existing grade intersects the wall. RW_Front will always be where proposed grade intersects the wall regardless of whether the wall is in cut or fill. The point codes swap places depending on what the condition is.

Finish by creating a composite surface. Paste the existing, proposed, and retaining wall surfaces into the composite surface in that order. Finish off the grading around the retaining wall area as necessary.

The contours in the wall can be masked with a hide boundary. Also, you can attach a daylight subassembly to the "hook-in" point to control grading from the retaining wall to the existing surface which is what I did in the above illustration.

05/03/2011

I'm aware that some people are bothered by the difficulty experienced in modeling pressure pipe in a pipe network. There are some out there using the corridor method by altering the pipe trench assembly.

I'd like to offer another workflow that is closely related to the corridor method.

1. Layout your pressure pipe as an alignment.

Create an alignment style that looks like your water line.

Create alignment line labels for labeling your water.

2. ﻿Create points to represent your structures.

﻿﻿Create blocks representing each structure and configure them to point styles.

Plan to use parameters in your description to label size i.e. TEE 8"x8" and manipulate the parameters in the full description for labeling purposes i.e. $1 TEE.

Certain point labels for the water structures will contain leaders and some will not. Those that do not contain leaders will be typically grouped under a leadered label.

Create a point group that will collect points with these descriptions.

3. Create a surface profile and profile view using your water alignment and the design surface.

Create a profile style that displays the properties of your water line in profile.

Sketch the top of pipe along the surface using profile layout tools.

Move the profile to the frost line using Raise/Lower PVI's.

Insert any pipe networks and existing utility locations that would affect the vertical design of the water line.

Insert PVI's as necessary to create vertical bends or deflections.

Use circular vertical curves with an appropriate value for radius if smoother pipes are desired.

Copy the top of pipe and move the resulting profile down the necessary amount to represent bottom of pipe.

There are a few reasons why I prefer this method:

Profile labels can be configured to call out station/elevation at regular intervals along the water line alignment even when the water line profile is superimposed onto a roadway centerline profile.

Curves to the water line can be applied and tolerated vertically.

Water structure points can be projected into the profile with station/elevation (projection) labels.

Assign elevations by creating a surface using the bottom of pipe. I find this to be a very simple task by creating a corridor surface. An assembly that contains one flat link projecting out a small distance will do the trick. A code set that displays nothing can be assigned to the corridor.

When projecting the points, assign elevations from the corridor surface and use point styles that display the structure appropriately for profile.

A few drawbacks:

Projection labels are only able to see raw descriptions. Edit Label Text will have to be used to revise.

If the projected point has been rotated in plan, the point will be rotated the same amount in profile; the symbol is rotated before Civil 3D applies any X-Y scaling from the point style. Keep insertion basepoint in center and manually adjust vertical locations after projecting. This will not change the actual point elevation.

If you desire to use the stretchy bow tie valve, project a point marker into profile and insert a dynamic block over the marker that stretches at the pertinent points.

If the bottom water line profile changes, the resulting corridor surface updates, but the projection labels containing elevations will not update. The points need to be deleted out of the profile and projected back in.